Queen Beatrix was wearing a gorgeous ring during the ceremony of the Silver Carnations of the Prince Bernhard Culture Fund in Amsterdam on June 18, 2013. The Silver Carnation is presented yearly since 1950, to persons who have contributed to culture or nature protection.
The ring is from the famous jeweller Royal Asscher (who cut the cullinan diamond) from the collection 'The Stars of Africa'.
Royal Asscher has confirmed to me that the ring is from their collection.
Photo from Royal Asscher. 18kt yellow gold with 1.20crt brilliants inside the dome